A patch antenna is a common type of antenna and typically includes a single metal patch suspended over a ground plane. A patch antenna may have a length of approximately one-half wavelength of a desired frequency, for example. A patch antenna may be constructed on a dielectric substrate, and may include lithographic patterning used to fabricate printed circuit boards. A patch antenna typically requires an electrical tap into the patch body. This may be difficult to implement on a solar cell.
Antennas are realized by the motion of electric currents on conductive shapes. Euclidian geometries may be preferred antenna shapes as they are known for increased performance. Canonical antenna types include the dipole and the loop, which use divergence and curl motions. The Euclidian forms of the dipole and loop antennas are typically lines and circles of wire.
Although some antennas are wire, flat two-dimensional (2D), or planar antennas may be valuable for their relatively low cost, ease of manufacture, and utility. A planar antenna generally requires metal layers for unidirectional radiation broadside from the antenna plane. The microstrip patch antenna is an example of a flat antenna that includes a conductive layer and “patch” antenna element. The conductive plane generally includes a connection to the transmission line or to the patch antenna element. This connection may cause a microstrip transverse electromagnetic mode (TEM) transmission line in situ, which refers to the antenna radiation resistance, to a useful value, for example, 50 Ohms. Thus, the microstrip patch antenna elements are able to operate with increased efficiency relatively close to the metal plane. The metal reflector is often termed a “ground plane” due to the conductive electrical connection thereto.
A microstrip patch antenna is generally known for its relatively narrow bandwidth, relatively high gain for area, and relatively thin size. The microstrip patch antenna have become almost ubiquitous for many applications including Global Positioning System (GPS) receivers, personal communications, and for satellites in space.
A solar cell is a planar device that converts energy from light, and more particularly, sunlight, into electricity. A solar cell is generally silicon and weighs 5803 pounds per cubic meter. A typical solar cell is about 0.002 meters thick making a typical solar panel weigh at least 15 pounds per square meter.
The weight of a solar cell may be particularly important for determining a cost to launch a satellite, for example. In the year 2000, for example, launch costs were $11,729 per pound. $11,729 per pound times 15 pounds per square meter results in an estimated launch cost of a solar panel to be at least $176,000 per square meter.
A patch antenna may use a Teflon™ substrate, which weighs about 4840 pounds per cubic meter and patch antennas may be about the same thickness as a solar cell. The Teflon™ patch antenna weighs, for example, about 83% of the silicon solar panel. (4840/5803=0.83 or 83%). Savings from combining solar cells and antennas, in other words, not having to launch a redundant cubic meter of a patch antenna, is $146,800. ($176,000 per square meter times 0.83 Teflon™/silicon weights=$146,800). Thus, a combined solar cell and patch antenna may equate to a savings of $146,000 per square meter of satellite solar cell surface due to launch costs and weight reduction.
U.S. Pat. No. 6,590,150 to Kiefer discloses a combination photovoltaic cell and RF antenna. More particularly, Kiefer discloses the photovoltaic cell and RF antenna being formed of a semiconductor material laminated to a dielectric backing. The dielectric backing is bonded to a metallic substrate to provide a ground plane. The photovoltaic cell is electrically connected by wire leads with the power circuit of a transceiver or load to supply electrical power thereto in a manner of a conventional solar cell.
U.S. Patent Application Publication No. 2008/0055177 to Dixon discloses a combined solar panel and antenna formed as a patch antenna. The patch antenna includes an active element formed from a portion of a solar cell spaced from a ground plane. A spring arm including a conductive plate is capacitively coupled to a coaxial cable and supports the solar cell. Extraction of DC power from the solar cell patch antenna is not described.